A STUDY OF THE PHOTODYNAMIC EFFICIENCIES OF SOME EYE LENS CONSTITUENTS

We have studied the photochemical quantum yields of singlet oxygen production (using the RNO bleaching method) and superoxide production (using the EPR-spin trapping method and the SOD-inhibitable ferricytochrome c reduction spectral assay) of kynurenine (Ky), N-formylkynurenine (NFK), 3-hydroxykynurenine (3HK), kynurenic acid (KUA), and the flavins, riboflavin (RF) and flavin mononucleotide (FMN). Such a study of the photodynamic efficiencies is important since these compounds appear endogenously in the eye. The singlet oxygen quantum yields of the flavins and KUA are high, while Ky and 3HK generate no detectable amounts of singlet oxygen. The superoxide quantum yields of the sensitizers are low compared to their singlet oxygen, and Ky and 3HK produce no detectable amounts of superoxide. The production of the superoxide radical is enhanced in the presence of electron donor molecules such as EDTA and NADH. These results suggest that the production of oxyradicals in the lens may be modulated by the presence of endogenous electron donor molecules such as the coenzymes NADH and NADPH, which are present in significant amounts in some lenses. They also suggest that Ky and 3HK, which are known to be present in aged lenses, might play a protective rather than a deleterious role in the eye.     

A further structural variation of product yield in collisional activation. Study of CH3S+ from dimethyl disulfide with high precursor ion resolution

The isobaric ions CH₃³²S⁺ and CH³⁴S⁺ from dimethyl disulfide were separated and collisionally activated in a four-sector mass spectrometer. The contributions of minor components to the collisional activation spectrum of the unresolved beam are not correctly predicted from consideration of isotope peak corrections using relative intensities of adjacent peaks in the mass spectrum of CH₃SSCH₃, because the isobaric components not only have different cross-sections for fragmentation but also different cross-sections for transmission of the unfragmented beam through the collision gas. Helium collision spectra of the two components are given.     

Zur Darstellung und Charakterisierung von Calciumhydrogensulfaten

Preparation and Characterization of Calcium Hydrogen Sulfate CaSO₄ · H₂SO₄ was identified as calcium hydrogen sulfate whereas CaSO₄ · 3 H₂SO₄ is an adduct of CaSO₄ with H₂SO₄. Depending on the excessive amount of H₂SO₄ both compounds exist side by side up to a temperature of 343 K, whereas above this temperature only Ca(HSO₄)₂ is stable. The DTA curve of Ca(HSO₄)₂ shows two maxima at 488 K and 523 K, according to the separation of H₂O under formation of pyrosulfate and decomposition of this compound under elimination of SO₃. In comparison with other hydrogen sulfates Ca(HSO₄)₂ shows a considerable increased O? H distances. The d-values of Ca(HSO₄)₂ are calculated and represented.     

Constant composition dissolution of mixed phases. II. Selective dissolution of calcium phosphates

Characterization of the dissolution kinetics of individual synthetic and biological calcium phosphates is of considerable importance since these phases often coexist in biological minerals. The constant composition method has been used to study the dissolution kinetics of a series of synthetic calcium phosphates, brushite (DCPD), beta-tricalcium phosphate (TCP), octacalcium phosphate (OCP), hydroxyapatite (HAP), and carbonated apatite (CAP) in the presence and absence of citric acid, as a function of pH and thermodynamic driving force. While citric acid markedly accelerates the dissolution of TCP, HAP dissolution is significantly inhibited. Moreover, this additive has almost no influence on the dissolution of DCPD, OCP, and CAP. Dual constant composition dissolution studies of mixed calcium phosphates in the presence of citric acid have also been made. Another factor, pH, also plays an important role in the dissolution of these calcium phosphates. In suspensions of calcium phosphate mixtures, specific phases can be selectively dissolved by changing experimental parameters such as pH and the presence of rate modifiers. This result has important applications for the dissolution control of dental hard tissues such as dentin, enamel, and calculus.     

Über eine temperaturbeständige und haltbare Trägerschicht für Elektroneninterferenzaufnahmen und übermikroskopische Untersuchungen

Ohne Zusammenfassung     

A correlation between fragment intensity and critical energy in collisional activation of some ions produced by electron impact

A Hammett correlation for ratios of intensities of collision induced fragments of [C₄R₄]^+· ions from tetraphenylcyclopentadienones is predicted on the basis of statistical theory and observed in practice.     

The Size of Spanning Disks for Polygonal Curves

   Abstract. For each integer n ≥ 0 , there is a closed, unknotted, polygonal curve K _n in R ³ having less than 10n+9 edges, with the property that any piecewise-linear triangulated disk spanning the curve contains at least 2 ^n-1 triangles.     

Theoretical studies on “acetylenic zipper” reaction intermediates

Nonempirical molecular orbital studies on a series of isomeric octyn-1-ols indicated that the anomalous stability of the alkoxide of 3-octyn-1-ol isomer is probably related to stereochemical and polarization properties of the molecule. The calculations correlated with the experimental observation that the least stable isomer should be the terminal alkyne, 7-octyn-1-ol.     

Unexpected course of olefin loss from some alkylcyclopentanone ions. Gaseous ion structure by ion cyclotron resonance spectrometry,mass-analyzed ion kinetic energy spectrometry and collision-induced dissociation

Ion cyclotron resonance results show that the ions formed by single and by double McLafferty rearrangement in 2-ethyl-5-propylcyclopentanone have neither keto nor enol structures. Collision-induced dissociations confirm that these ions are structurally distinct from the keto ions formed directly by electron impact upon the corresponding neutral molecules. It is suggested that the major reaction path for olefin loss from 2-ethyl-5-propylcyclopentanone and from 2-ethylcyclopentanone involves ring opening followed by hydrogen transfer to carbon in the alkene elimination step. Only in metastable ions is there evidence for the occurrence of the normal McLafferty rearrangement. The techniques mentioned in the title, together with conventional low and high resolution mass spectrometry, have been used to characterize the sometimes complex mixtures of cyclic and acyclic ions formed from cyclopentanone and some of its alkyl derivatives. Use of a number of different techniques of ion structure characterization allowed corroboration of particular results by quite distinct methods and it also allowed the effects of ion internal energy and lifetime upon structure to be partly elucidated.     

On finiteness of the number of boundary slopes of immersed surfaces in 3-manifolds

For any hyperbolic 3-manifold with totally geodesic boundary, there are finitely many boundary slopes for essential immersed surfaces of a given genus. There is a uniform bound for the number of such boundary slopes if the genus of is bounded from above.